The present invention relates to the use of hydrophobic bleaching systems to prepare textiles for finishing and, more particularly, to the use of activated peroxide bleaching via hydrophobic activators or hydrophobic peracids to prepare woven or knitted fabrics, fibers or yarns for application of durable press as well as the textiles produced therefrom.
In the textile processing of natural fibers, yarns and fabrics, a pretreatment or preparation step is typically required to properly prepare the natural materials for further use and in particular for the dyeing and/or finishing stages typically required for commercial goods. These textile treatment steps remove impurities and color bodies, either naturally existing or those added by the spinning and weaving steps to the fibers and/or fabrics.
A common pretreatment step for preparing textiles for finishing involves a bleaching step to destroy naturally occurring color bodies and is necessary for commercially acceptable consumer fabrics. Traditional textile bleaching of natural fibers has involved the use of hydrogen peroxide. Hydrogen peroxide has gained its wide acceptance due to its flexibility of use being capable in both hot and rapid or cold and long dwell bleaching processes and due to its environmental friendliness.
While hydrogen peroxide has gained wide spread acceptance in the textile industry, it is not a particularly effective bleaching agent. Hydrogen peroxide, as commercially supplied, is an extremely stable compound and as a result has only a slight bleaching effect on natural fibers. To overcome its weak activity, extremely high temperatures and/or extremely long bleaching times are required in commercial processes in addition to activation of the peroxide. That is, temperatures in excess of 95xc2x0 C. are typically required. In addition, activation of the peroxide via the use of alkali, sulfuric acid, uv irradiation, hypochlorite or organic activators is also necessary with alkali being the most preferred. Not only do these drawbacks result in excessive cost associated with commercial textile peroxide bleaching, but the high temperatures and/or long contact times result in significant fiber damage and strength reduction of the resultant yarns and fabrics.
These drawbacks, in particular, fiber damage and fabric strength reduction, when combined with a durable press application are exacerbated. A number of processes are known for treating textiles to make them wrinkle-free or provide them with durable press benefits including resin or polymer treatments as well as formaldehyde crosslinking. Conventional formaldehyde durable press treatment involves saturating the textile with an aqueous solution of formaldehyde and acid catalyst followed by heat curing at high temperature to crosslink the formaldehyde to the textile. However, the combination of curing at high temperature and an acid catalyst results in an unacceptably high loss in fiber strength.
Accordingly, the combination of conventional peroxide bleaching technology with conventional durable press technology will result in unsatisfactory textile properties. Thus, the need remains for a simple, reproducible, effective and low cost process for the preparation and durable press finishing of textiles.
This need is met by the present invention wherein a method for the preparation and application of durable press to textiles is provided. Textile substrates produced from the method are also provided. The method involves the treatment of textiles using activated peroxygen bleaching via hydrophobic bleaching agents followed by application of a durable press finish. The bleaching aspect of the present invention involves the use of hydrogen peroxide and a hydrophobic bleaching agent such as an activator or a hydrophobic peracid while the durable press step involves the application of a durable press via cross-linking technology such as resins or formaldehyde. In the preferred durable press treatment of the present invention, an aqueous solution of formaldehyde, catalyst and silicone elastomer forming material is employed to saturate the textile followed by curing.
The use of a hydrophobic bleach species provides superior fabric strength and fiber damage benefits, i.e. strength retention to fibers, yarns and fabrics, in addition to significant cost reduction in the operation of the bleaching step through the use of significantly lower bleaching temperatures than conventional peroxide bleaching and much shorter processing times, particularly in batch processing.
While not wishing to be bound by theory, it is believed that in the bleaching step of the present invention, the hydrophobic bleach species of the present invention provide better absorbency on the fabrics and yarns and better xe2x80x9cwettingxe2x80x9d of the surface of the fibers than conventional peroxide bleaching techniques or hydrophilic activators. Hydrophobic bleach activators form the active bleaching species, peracid, on the surface of the fabric allowing a longer time on the surface of the fabric. Hydrophilic activators, meanwhile, form peracid in solution and must then undergo a fabric solution interaction which is less efficient. As a result, the hydrophobic activators of the present invention provide superior bleaching and whiteness while minimizing fiber damage and fabric strength reduction.
Again, while not wishing to be bound by theory, it is believed that in the preferred durable press step of the present invention, the unique presence of the silicone elastomer in the durable press finish provide improved fiber strength benefits versus conventional durable press methods. Thus, the combination of the hydrophobic bleaching and the durable press of the present invention, lead to a textile with superior fiber strength properties in comparison to like textiles treated via conventional technology. The textiles provided via the present method have superior whiteness in addition to strength retention as well as superior wettability.
According to a first embodiment of the present invention, a method for the treatment of non-finished textile components is provided. The method comprises the steps of providing a non-finished textile component such as a fiber, yarn or fabric, saturating the textile component with an aqueous bleaching solution comprising hydrogen peroxide and a hydrophobic bleaching agent such as an activator or a pre-formed hydrophobic peracid, and allowing the bleaching solution to remain in contact with the textile component for a period of time sufficient to bleach the textile component followed by finishing the textile component with the application of durable press. The preferred durable press application step includes treating the textile with an aqueous solution of formaldehyde, a catalyst capable of catalyzing a cross linking reaction with the textile and an effective amount of a silicone elastomer forming material and curing the treated textile to form durable press in the textile component. Alternatively preferred in the present invention is a durable press application comprising treating the textile with a solution of an alkylene urea and a catalyst capable of crosslinking the urea on the textile.
In preferred embodiments, the bleaching solution comprises hydrogen peroxide and a hydrophobic bleach activator which is selected from the group consisting of:
a) a bleach activator of the general formula: 
wherein R is an alkyl group having from about 5 to about 17, preferably from about 8 to about 11, carbon atoms and L is a leaving group;
b) a bleach activator of the general formula: 
or mixtures thereof, wherein R1 is an alkyl, aryl, or alkaryl group containing from about 1 to about 14 carbon atoms, R2 is an alkylene, arylene or alkarylene group containing from about 1 to about 14 carbon atoms, R5 is H or an alkyl, aryl, or alkaryl group containing from about 1 to about 10 carbon atoms, and L is a leaving group;
c) a benzoxazin-type bleach activator of the formula: 
wherein R1 is H, alkyl, alkaryl, aryl, arylalkyl, and wherein R2, R3 R4, and R5 may be the same or different substituents selected from H, halogen, alkyl, alkenyl, aryl, hydroxyl, alkoxyl, amino, alkylamino, xe2x80x94COOR6, wherein R6 is H or an alkyl group and carbonyl functions;
d) a N-acyl caprolactam bleach activator of the formula: 
wherein R6 is H or an alkyl, aryl, alkoxyaryl, or alkaryl group containing from 1 to 12 carbons; and
e) mixtures of a, b, c and d with the alkanoyloxybenzenesulfonates of the formula: 
wherein R1 is an alkyl group having from about 8 to 11 carbon atoms and M is a suitable cation being the most preferred hydrophobic activators.
In optional embodiments, the bleaching solution further includes an ingredient selected from the group of wetting agents, sequestering agents, stabilizing agents, de-sizing agents, scouring agents and mixtures thereof. Preferred ranges of peroxide and activator are from about 1 g/L to about 20 g/L hydrogen peroxide with a molar ratio of hydrophobic bleach activator to hydrogen peroxide of from about 1:1 to 1:50.
The textile components remain in contact with the bleaching solution at a temperature of from about 20 to about 80xc2x0 C., preferably from about 50xc2x0 C. to about 80xc2x0 C. and for a period of time suitable for whitening the textile component which is typically at least about 15 minutes, more preferably from about 15 minutes to about 180 minutes, and even more preferably from about 30 to about 60 minutes. In preferred operations, the textile component experiences a fabric strength reduction of less than about 10% and more preferably less than about 5% due to the bleaching of the present invention. Alternatively, the textile component experiences a fluidity increase of less than about 25%.
In preferred embodiments of the durable press step the curing is a heat curing and is carried out at a temperature of from about 250xc2x0 F. to about 325xc2x0 F. while the textile is immersed in a treatment solution which preferably provides a solution pick up, on weight of fabric, of at least about 3% formaldehyde, at least about 1% catalyst and at least 1% silicone elastomer forming material and a preferred catalyst of magnesium chloride containing citric acid.
Accordingly, it is an object of the present invention to provide a method for the application of durable press finish to textile components such as fibers, yarns and fabrics without a significant reduction in fabric strength, and potential fiber damage common to conventional preparation processes. It is another object of the present invention to provide a method for the application of durable press finishes to textiles involving the use preparation step employing a hydrophobic bleach activator or pre-formed peracid in conjunction with hydrogen peroxide. These, and other objects, features and advantages of the present invention will be apparent from the following detailed description and the appended claims.
All percentages, ratios and proportions herein are on a 100% weight basis unless otherwise indicated. All documents cited herein are hereby incorporated by reference.